In various applications (optimal control, stability analysis) one is interested in establishing differentiability of the solution to the perturbed problem with respect to perturbation size. In this talk, we consider measure solutions to perturbed structured population model. We show that differentiability result is not possible in the so far used flat metric setting. Therefore, we move to bigger space and show that under sufficient regularity assumptions, derivative exists. The talk is based on the recent preprint https://arxiv.org/abs/1812.01747.